Hawai`i's Oldest Volcano
Photo by J. Kauahikaua on August 26, 1994
Kohala Volcano is the oldest of Hawai`i's five subaerial volcanoes and probably emerged above sea level more than 500,000 years ago. Toward the end of its shield-building stage 250,000 to 300,000 years ago, an enormous landslide removed the volcano's northeast flank. Twenty kilometers wide at the shoreline, the landslide cut back to the summit of the volcano, which at the time was just over 1,000 m higher than today, and traveled 130 km across the ocean floor. The famous sea cliffs of windward Kohala shoreline mark the topmost part of the headwall of this ancient landslide.
When eruptions had built Kohala's broad shield to its greatest extent, the volcano was more than twice as wide as it is today. Based on an abrupt change in angle of the submarine slope at a depth of about 1,000 m, scientists estimate the subaerial part of the island at this time was more than 50 km wide. Then, when the rate of eruption decreased more than 300,00 years ago, the slow subsidence of the Island outstripped the rate of growth of the volcano, which slowly began to sink beneath sea level. But to the southeast, lava flows from Mauna Kea and Mauna Loa buried the southern flank of Kohala.
The broad forest-covered summit of Kohala consists of many cones that erupted along its two rift zones between about 240,000 to 120,000 years ago.
There is no literal Hawaiian translation for Kohala, which is the name of a district of northern Hawai`i.
Kohala Volcano Facts
Map of the Island of Hawai`i
20.08 N 155.70 W
Elev. Above Sea Level
(5.8% of Hawai`i)
3,400 cu mi3
Most Recent Eruption(s)
About 120,000 years ago
Number of Historical Eruptions
Oldest Dated Rocks
About 460,000 years before present
Estimated Age of Kohala
Emerged above sea level before 500,000 years ago
Hawaiian Volcano Stage
Transition between postshield and erosional stage
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20 March 1998 (pnf)